This invention relates to guardrail posts, and more particularly to guardrail posts which are adapted to meet environmental as well as safety concerns. Due to the widespread use of guardrails along highways, various governmental bodies have developed standardized criteria for guardrails. Factors considered important in the development of those criteria are: the design loadings, design life of a guardrail post exposed to the elements, initial cost, replacement cost, installation method, and vehicle occupant safety upon collision with the guardrail.
The improved guardrail post of the present invention is designed to hold a W-shaped steel guard rail in position with the same strength as a conventional southern white pine post. The present invention will also support other types of guardrails, including those made of other materials, such as composites, and those made in other than the typical "W" shape. The design life of the improved guardrail post will be equal to or greater than that of conventional treated wood posts and galvanized steel posts. Furthermore, the improved guardrail post can be installed by methods currently used for conventional wood and steel posts. The preferred embodiment of the invention can withstand sufficient impact to be driven into the ground in the same manner in which wood guardrail posts are installed.
As important as the design criteria is the fact that new Environmental Protection Agency (EPA) requirements are becoming increasingly larger obstacles to the continued use of wood or steel posts. Because the wood posts are chemically treated to provide better weather and insect resistance, they cannot be disposed of by burning or burying in landfills. The disposal of steel posts is similarly restricted by EPA regulations because of the heavy metal galvanizing required for weather and corrosion resistance. In addition to restrictions on disposal, the use of wood posts is limited by the availability of wood itself. Some states have already encountered shortages of guardrail posts due to limited sources of wood and deforestation concerns.
Although the environmental dangers of the use of wood and steel guardrail posts are not recent developments, public concern over such dangers is relatively new. Notions of using composites in this area in the past had been readily dismissed due to the availability of conventional materials and the indifference to the dangers. With the increasing public awareness of environmental concerns, however, it has become apparent that the present invention is a solution to the dangers posed by prior art guardrail posts.
The prior art includes the following patents: U.S. Pat. No. 3,709,112 to Ebinger; U.S. Pat. No. 3,820,906 to Katt; U.S. Pat. No. 4,092,081 to Schmanski; and U.S. Pat. No. 4,939,037 to Zion and Freeman.